There’s a lot to discuss from your questions. Some of it depends on what your intentions are for the exports. It seems like you are wanting to export and sell child themes so I will answer from that perspective.
Child Theme files are not created by Easy Demo Import. My recommendation is for you to learn how to create your own child theme files. Since it is a product you intend to sell, it makes sense that you fully understand how that works.
The free version doesn’t exist any longer. You can export as a theme or plugin from the paid version.
For images, there are no license requirements as far as Easy Demo Import is concerned. There are potential license issues if you are distributing/selling a product containing images that are not CC0 or that you do not have license to distribute. The issue would be with the license holder, not with the plugin. And ET does have requirements for images included in the products sold in their marketplace. To help with this, Easy Demo Import allows you to export placeholder images in place of the actual images used in the demo site.
Hope that helps a little.